Typing into 'large' QTextFrames very slow

If there is a QTextFrames frame contains a lot of text (many lines of text), typing towards the end of the frame gets too slow. This behavior can be seen in the textedit demo: within a table cell, type a long paragraph of text (e.g. <table><tr><td> lots of text...</td></tr></table>)

Update: this will probably require quite large changes to the way we do layouting, and thus we can't commit to a specific release at the moment